Saturable reactor regulator



March 29, 1949. s. E. HEDSTRUM ET AL 2,465,451

SATURABLE REACTOR REGULATOR Filed Aug. 16, 1947 //7 Wm f0 r5 Y? n N 2/ 80m) Hey Patented Mar. 29, 1949 SATURABLE REACTOR REGULATOR Sven Eric Hedstriim and Arne Siiderholm, Ludvika, Sweden, assignors to Allmiinna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden Application August 16, 1947, Serial No. 769,028

. In Sweden August 27, 1946 6 Claims. 1

Self-magnetized direct current saturable reactors-hereinafter referred to as transductorsare at present, as a rule, provided with socalled internal self-magnetisation, which implies that certain transductor elements, in some cases all such elements, are directly series-connected with valves which admit only a part of each alternating current wave through the transductor element. Such a connection operates substantially in the same manner as direct current ampereturns superposed on the alternating current ampereturns and being of the same order of magnitures as the latter ones, i. e. as an external self-magnetisation with direct current ampereturns nearly corresponding to those of the alternating current, such self-magnetisation being usually designated as a hundred percent one. There is, however, frequently a need of adjusting the self-magnetisation in relation to that obtained in the said manner, which is more or less tied to the properties of the valves employed. The most obvious step for this purpose, especially when the transductor is loaded by direct current, is to place thereon some additional winding turns traversed by the rectified load current. Another previously known step, which can be used also when the load current is not rectified, is to cause some winding turns on each transductor element to be traversed by an alternating current derived from another wave portion of the main current than that traversing the main winding of the element. The present invention chooses a third way which offers better possibilities of a Convenient regulation of the additional self-magnetisation than those previously proposed. According to the invention, the additional selfmagnetisation is obtained by means of a. winding connected in parallel to a resistance traversed by the main current of the transductor. The resistance may consist of the main winding itself of the transductor or of a part thereof, in which case it should be observed, that the current serving the additional magnetisation is a (more or less pulsating) direct current, whence the winding acts, with respect to this current, not as an inductance but essentially as an ohmic resistance.

Some forms of the invention are diagrammatically illustrated in the accompanying drawing in Figs. 1-3 and 5, while Fig. 4 is a. diagram of the manner of operation of the form according to Fig. 3.

In Fig. 1, the numerals I and 2 designate the two main windings of a transductor which further may have one or more control windings, not shown. Each of the windings I and 2 is connected in series with a unidirectional valve 3, 4 respectively, and between these valves one terminal of an alternating current source is con nected, while between the other alternating current terminal and the windings I, 2 resistances 5, 6 are connected. Eachvalve 3, 4 admits only one half of each alternating current wave, so that in the closed circuit through the valves, the windings i, 2 and the resistances 5, 6, a (pulsating) direct current flows. This current causes a voltage drop between the points I, 8. Between these points there are connected, in parallel to the resistances 5, 6, a pair of windings 9, I0 on the two transductor cores and in series with these an adjusting resistance 6 B. By means of these members, an adjustable direct current magnetisation can be imparted to the transductor cores in addition to that produced by the main windings l, 2. This additional magnetisation is proportional to the main current and has thus the character of a self-magnetisation.

Fig. 2 differs from Fig. 1 in that the additional windings H, Ill and their adjusting resistance II are connected directly in parallel with the main windings I, 2 instead of with resistances in series with these. The action will be identical in principle, as the windings i, 2 and 9, I0 behave like ohmic resistances with respect to the direct current. The windings may for instance have nearly the same number of turns or, more precisely, the additional windings may have a slightly higher number than the main windings I, 2 and at any rate with a smaller sectional area corresponding essentially to the smaller current. The windings 9, ill may instead be connected in parallel to only a portion of the main windings, for instance to one half of these, which as a rule does not necessitate any additional tap, as the main windings are generally divided on two core legs each.

In Fig. 3, the additional windings 9, I II are as in Fig. 2 connected in parallel to the main windings I, 2, but the adjusting resistance, which is here designated by I2, is connected in a bridge between the additional windings and the valves 3, 4, so that the latter can be more or less shortcircuited by its adjustment at the same time as a larger or smaller portion of the resistance is connected in series with the windings 9, III. The

result hereof is illustrated by the curve group in Fig. 4, in which the different curves represent the controlled transductor current as a function of the controlling ampereturns for different adjustments of the resistance I2. The lowest curve represents full short-circuit of the valves 3, l, i. e. no self-magnetisation of the transductor. As

more resistance is in parallel to the valves 3,14 and less resistance in serieswith the windings'9, ll, the curves will be more and more steep until the. topmost curve which corresponds to what is generally designated as more than hundred percent self-magnetisation, whereby the current in-practice changes intermittently from a low to a high value and vice versa, following minals, between which an adjusting resistance 39 is connected. The additional windings are, however, so connected that for instance the winding 34, shunting the main winding 2| and thus carrying current simultaneously with the latter, is mounted on the core of thewinding 22 which lags behind the winding 2| in phase. The additional magnetisation of each winding thus appears before the main magnetisation, whereby its action will be most eflicient. Instead of mounting the additional winding parallel to the main winding 2| on the core of the winding 22, it can be mounted on the core of the winding 26, which begins to carry a current a sixth part of a cycle after the winding 2i.

We claim as our invention:

1. A direct current saturable reactor for connection to a source of alternating current which comprises a pair of terminals adapted to be connected to such source, means forming two parallel current paths between said terminals, each of said paths including a reactor winding, a core for each of said windings, a rectifier valve in each of said paths in series with the winding therein, said valves admitting current in different directions through the two paths, and means forming a current path'shunting at least parts of said first two paths, said last path including additional windings one on each of said cores.

2. A direct current saturable reactor comprising two reactor windings connected in par-allel between alternating current terminals, magnetic cores for said windings, rectifier valves connected in series with said windings and admitting current in different directions through the different parallel windings, a resistance adapted to be traversed by the unidirectional current traversing said windings in series, and additional windings 3. A direct current saturable reactor comprising two reactor windings connected in parallel between alternating current terminals, magnetic cores for said windings, rectifier valves connected in series with said windings and admitting current in different directions through the diiierent parallel windings and additional windings on the cores of said reactor windings connected in parallel to at least part of said first-mentioned wind- 4. A direct current saturable reactor comprising two reactor windings connected in parallel between alternating current terminals, magnetic cores for said windings, rectifier valves connected in series with said windings and admitting current in different directions through the diflerent parallel windings, a resistance adapted to be traversed by the unidirectional current traversing said windings in series, additional windings on said cores, and an adjustable resistance in series therewith connected in parallel to said firstnamed resistance.

5. A direct current saturable reactor comprising two reactor windings connected in parallel between alternating current terminals, magnetic cores for said windings, rectifier valves connected in series with said windings and admitting current in diflerent directions through the different parallel windings, additional windings on the cores of said reactor connected in parallel to at least part of said first-mentioned windings, and

, an adjustable resistance having one portion connected in series with said additional windings and one portion in parallel with said valves.

6. A direct current saturable polyphase reactor comprising for each phase two reactor windings connected in parallel between alternating current terminals, magnetic cores for said windings, rectifier valves connected in series with said windings and admitting current in diflerent directions through the difierent parallel windings, and an additional winding on each 01' said cores connected in parallel with at least part or one 0! said first-named windings mounted on another 1 The following references are of record in the file of this patent:

UNITED STATES PATENTS Date Number Name 2,169,093 Edwards Aug. 8, 1939 2,403,891 Lamm July 9, i946 

